Transmission line measuring device and method for connectivity and monitoring

ABSTRACT

A method for connecting low power radios into a self-assembling and self-healing network with multiple portals to higher speed networks such as, but not limited to, electrical or optical Ethernet is provided for monitoring transmission lines, for example. A clamp or other device is provided that includes an integral or associated current transformer and associated circuitry with design elements to address high temperature operation or other operating parameters. An arrangement of sensors is provided (e.g., sensors can be associated with clamps or positioned along infrastructure being monitored and without dependence on any clamps or other devices) that are designed to communicate and operate in an geographically distributed array to provide increased and autonomous monitoring of large utility, highway, communication and similar networks. A unique collection of sensors (e.g., an anemometer with no moving parts) provides comprehensive diagnostics for improved operation of large geographic scale utility, highway, communication and similar infrastructure.

This application is a national stage application which is based on PCTApplication No. PCT/US2011/01632, filed Sep. 22, 2011, which claimspriority to U.S. Provisional Patent Application Ser. No. 61/385,320,filed Sep. 22, 2010; the entire contents of each application beingincorporated herein by reference.

FIELD OF THE INVENTION

The present application relates to data collecting and, moreparticularly, to a connector (e.g., data acquisition suspension clamp)for an electrical conductor or other transmission line (e.g., a powertransmission line, a communications line, a gas line, a water line, anoil line, a railroad, a highway, among others that are deployed overgeographic distances) which collects data and reports measuredconditions of the conductor or transmission line to a monitoring deviceor systems. However, illustrative embodiments of the present inventionneed not be restricted to use as part of a clamp. For example,embodiments of the present invention can be implemented at a locationnext to a clamp or implemented without dependence upon any clamp orother device.

BACKGROUND OF THE INVENTION Power Grids

FIGS. 1-4 illustrate related art disclosed in U.S. Pat. No. 8,002,592.FIG. 1 shows a transmission tower 200 which is used to suspend powertransmission lines 202 above the ground. The tower 200 has cantileveredarms 204. Insulators 206 extend down from the arms 204. One or moresuspension clamps 208 are located at the bottom ends of the insulators206. The lines 202 are connected to the suspension clamps. The clamps208 hold the power transmission lines 202 onto the insulator 206.

FIGS. 2-4 illustrate an example embodiment of the suspension clamp 208which generally comprises an upper section 210 and a lower supportsection 212. These two sections 210, 212 each contain a body 214, 216which form a suspension case. The bodies 214, 216 each comprise alongitudinal trough (or conductor receiving area) 215, 217 that allowthe transmission conductor 202 to be securely seated within the twosections and when the two sections are bolted (or fastened) together bythreaded fasteners 201 (not shown). This encases the transmissionconductor 202 between the two bodies to securely contain thetransmission conductor 202 on the clamp 208. Threaded fasteners are notrequired and any other suitable fastening configuration may be provided.

The two bodies 214, 216 connected together are suspended via a metalbracket 218 that attaches to the lower body 216 at points via bolthardware 220.

The lower body, or lower body section, 216 comprise a first end 219 anda second end 221. The conductor receiving area (or conductor contactsurface) 217 extends from the first end 219 to the second end 221 alonga top side of the lower body 216. The conductor receiving area 217 formsa lower groove portion for contacting a lower half of the conductor 202.A general groove shape is not required, and any suitable configurationmay be provided.

In one implementation, the upper and lower sections 210, 212 each haveimbedded within their respective bodies 214, 216 one-half of a currenttransformer 222, 224 that is commonly referred to in the industry as asplit core current transformer. When these components 222, 224 arejoined, they form an electromagnetic circuit that allows, in someapplications, the sensing of current passing through the conductor 202.In one implementation, the current transformer is used to power sensing,data collection, data analysis and data formatting devices. In someimplementations the current transformer may be located outside of theclamp or similar device or, in some implementations, power may beprovided by another means.

The body 214 of the upper section 210 contains a first member 232 and asecond member 234 forming a cover plate. The first member 232 comprisesa first end 233, a second end 235, and a middle section 237 between thefirst end 233 and the second end 235. The conductor receiving area (orconductor contact surface) 215 extends from the first end 233 to thesecond end 235 along a bottom side of the first member 232. Theconductor receiving area 215 forms an upper groove portion forcontacting an upper half of the conductor 202. A general groove shape isnot required, and any suitable configuration may be provided. In oneimplementation, the first member 232 further comprises a recessed cavity226 at the middle section 237 that effectively contains an electroniccircuit 228. In this implementation, the electronic circuit 228 isdesigned to accept inputs from several sensing components. This cavity226 may be surrounded by a faraday cage 230 to effectively nullify theeffects of high voltage EMF influence from the conductor 202 on thecircuitry 228. The faraday cage may also surround the currenttransformer 222. The cover plate, or cover plate member, 234 can coverthe top opening to the cavity 226 to retain the electronic circuitinside the body, or upper body section, 214. The electronics may behoused in a metal or plastic container, surrounded by the noted faradaycage, and the entire assembly can be potted, such as with epoxy forexample.

The electronic circuit 228 can accept and quantify in a meaningfulmanner various inputs for monitoring various parameters of the conductor202 and the surrounding environment. The inputs can also be derived fromexternally mounted electronic referencing devices/components. The inputscan include, for example: 1) Line Voltage reference (as derived from thefaraday cage 230 or other means); 2) Line Current reference (as derivedfrom the Current transformer 222, 224 or other means); 3) Barometricpressure and Temperature references—internal and ambient (as derivedfrom internal and external thermocouples 236, 238 or other means); 4)Vibration references of the conductor (as derived from the accelerometer240, such as a 10-150 KHz vibration sensor for example, or other means);and 5) Optical references (as derived from the photo transistor 242 in afiber optic tube or other means). The optical reference portion may, forexample, allow the clamp to look up and see flashes of light from coronaif the insulator starts to fail, or lightening indication stormactivity, and/or tensile references (as derived from the tension straindevice 244 which may be included in certain implementations). Thetensile references from the tensile indicators 244 may, for example,provide information indicating that ice is forming as the weight of theconductor increases due to ice build up.

Supervisory Control And Data Acquisition (SCADA) generally refers to anindustrial control system such as a computer system monitoring andcontrolling a process. Information derived by the electrical/electroniccircuitry can exit the circuit 228 via a non-conductive fiber opticcable 246 and be provided up and over to the transmission tower 200 andultimately at the base of the tower and fed into the user's SCADA systemto allow the end user to access and view electrical and environmentalconditions at that sight, or the information can be transmitted to aremote or central site. This implementation, however, has proven to beproblematic. For example, routing fiber to a clamp that is operating atvery high voltage creates a voltage creep path that can cause an arceven though glass fiber and plastic sheath are provided as insulators.Arcs form along the boundary between the air and the solid insulator. Ifthe insulator were just a simple rod, it would have to be 3 timeslonger. The suspension clamp or other sensing device may bealternatively configured to wirelessly transmit information from theelectronic circuit 228 to a receiver system. However, thisimplementation has likewise been problematic due to the complexity ofthe software needed to accommodate the distances over which the clampsare used and the number of clamps being monitored.

Certain Problems can Occur in Current Grids

Transmission lines face numerous problems. Wind causes vibration whichcan gradually crack the wire or destroy it outright. Excessive heat maycause lines to sag into trees or traffic. Corroded wires will generatemore heat when current passes through, but there is no way to know theextent of any corrosion since it is generally interior to the wire.Corona is a type of electrical discharge which will eat away at wire,insulators, and anything else in the vicinity. Ice buildup can breakwire due to the weight. Trees may fall naturally over wires and pose ahazard if not trimmed. Natural and man-made disasters, such asearthquakes and forest fires can damage transmission power lines. Inaddition, wildlife, and squirrels in particular, can get carbonized whenthey crawl into certain components of a power grid, thereby causingdisruption of power transmission via the power transmission lines. Lineoptimization to boost capacity is temperature dependent and can only bedone via conservative estimates of local conditions.

Grid Monitoring

In conventional power grids, current and voltage are measured atsubstations. Current capacity of a line is estimated based on the wirediameter, age of the wire, the ambient temperature, and wind speed.However, due to many variables, it is an educated guess. In addition,there is no early warning with regard to ice build-up and ice isdetected when a wire breaks during icing. Vibration dampers areroutinely attached to the power lines to reduce vibration; however,their effectiveness is only estimated by how many lines break due tovibration stress, in spite of the dampers being present. The power linescan generate corona that can be heard as a sizzling sound and can alsobe seen by using special cameras that can see in the ultravioletspectrum. However, such cameras are large and expensive. The cameras aregenerally sent to places where someone has heard a sizzling sound orwhere an insulator appears to be eaten away but may not be effectivesince corona can be intermittent and is affected by many environmentalconditions such as moisture and air pressure. Further, most proposedtelemonitoring devices require battery power. Battery power is notsuitable in these applications that are elevated above ground anddistributed over large geographic areas, making their maintenanceuntenable. In addition to powering challenges, existing monitoringdevices are relatively expensive and large, which limits their use tooccasional applications or installation to limited sites. As a result,there is no opportunity to gather widespread data and makedeterminations such as lightning location by way of triangulation orreal-time power carrying capacity based upon full transmission lineweather conditions.

Repair or Servicing a Transmission Line

Initially, one must locate where a power transmission line is broken.However, power transmission lines can run hundreds of miles betweensubstations, and the only information generally available is that onesubstation is supplying power and the next one is not receiving thesupplied power. Accessibility to power transmission lines may vary. Insome cases, the power transmission lines may be accessible by motorizedground vehicles. In other cases, lines may only be accessible byhelicopter, wherein a service technician must hang under the helicopterto service or repair a line. Such repairs or maintenance can be veryexpensive.

Communication Issues

In order to retrieve information about the system, rapid and securecommunication is necessary. Radio communication via Ethernet is oneoption. However, organizing an Ethernet network requires the use ofdevices known as routers or switches. Each router or switch will look atan Ethernet packet of information and make note of the source addressand the destination address as the packet arrives at a port. If thedestination is known, the packet is forwarded to only one port which isknown to be connected to that destination device. If it is not a knownaddress, it is repeated to all ports except the port where it arrived.When the destination device responds, the source address will appear ina packet on a single port which permit the router or switch to learnwhere to send the next packet with that particular destination address.

There are specific protocols which optimize the route for delivering apacket and to remove the opportunity for a packet to become repeated ina loop in the network. Some of the more common protocols are SpanningTree Protocol and Rapid Spanning Tree Protocol.

A popular radio protocol for packet-based transmission is Zigbee whichis described in standard IEEE 802.15.4. It is intended for relativelysmall radio networks in a small geographic area. It is well suited to asingle building or a property of several acres. However, when the radiosbecome numerous and spread out over a large area, the system becomesunworkable. The most distant radio message must be repeated bycoordinator elements (e.g., a more capable radio) until the destinationis reached. Because there is a time limit for a reply, the physicaldimensions of the network are limited.

Although devices exist for monitoring transmission lines, they face thepowering, diagnostic and communication challenges noted above. There isa need for a system that allows for fast analysis of any actual orpotential repair problems and power optimization capabilities alongtransmission lines (e.g., to permit, for example, increased peak loadsbased upon real operating conditions versus conservative estimates basedupon worst case weather), with lower costs of repair, betterpreventative maintenance, and faster restore times. Further, there is aneed for a simple way of communicating and collecting the substantialamount of data that can be accumulated by a wide-spread installation ofsensing devices over large geographic areas.

SUMMARY OF THE INVENTION

Illustrative embodiments of the present invention address at least theabove problems and/or disadvantages, and provide at least the advantagesdescribed below.

In according to illustrative embodiments of the present invention, amethod of data collecting and a data acquisition device for anelectrical conductor or other transmission line (e.g., a powertransmission line, a communications line, a gas line, a water line, anoil line, a railroad, a highway, among others that are deployed overgeographic distances) are provided to collect data and report measuredconditions of the conductor or transmission line to a monitoringdevice(s) or system(s). The data acquisition device is illustrated inconjunction with a clamp; however, illustrative embodiments of thepresent invention need not be restricted to use as part of a clamp. Forexample, embodiments of the present invention can be implemented using adata acquisition device at a location next to a clamp or implementedwithout dependence upon any clamp or other connection device.

In accordance with illustrative embodiments of the present invention, adata acquisition device is implemented as a smart clamp that holds atransmission line conductor to a high voltage insulator. A split corecurrent transformer in the center of the clamp or near the clampharvests approximately 5 watts (W) to power measuring and sensorcircuitry. The two halves of the split core current transformer arejoined during clamp installation or during a separate installationprocess. Communication and sensor electronics (e.g., a GPS device andradio) are housed in a non-metallic enclosure on the side of the smartclamp. The non-metallic material facilitates proper radio and GPSoperation. A “T-shaped” extension at the bottom of the enclosure housesambient air temperature and wind speed detectors. Wind measurement isdone without moving parts to help assure long-term reliability, andfeatures unique two-stage technology to improve the accuracy oflow-speed and high-speed wind velocity measurements. A smart grid can beimplemented using a multi-hop short range radio system to relayinformation between data acquisition devices provided along the line toone or two ground-based adaptors that convert the information to astandard electrical or optical Ethernet interface. Each clamp's radiohas an approximate line-of-sight range of about 1 mile and is operatedin accordance with a protocol for participating in multi-hop short rangeradio communications. Each clamp is configured to send a message (e.g.,a short e-mail message) to programmable e-mail addresses in case ofevents such as current surges, excessive conductor temperature,excessive vibration, corona, and the like to ensure rapid andintelligent response to serious conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other exemplary features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of certain exemplary embodiments thereof when taken inconjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of a transmission tower supportingtransmission lines connected via suspension clamps;

FIG. 2 is a perspective view of a suspension clamp;

FIG. 3 is a cross section view of the suspension clamp shown in FIG. 2;

FIG. 4 is a perspective view of a first member of the suspension clampshown in FIG. 2;

FIG. 5 is a perspective view of a smart clamp constructed in accordancewith an illustrative embodiment of the present invention;

FIG. 6 is an exploded perspective view of the smart clamp of FIG. 5;

FIG. 7 is a top view of the clamp body of the smart clamp of FIG. 5;

FIG. 8 is a bottom view of the smart clamp of FIG. 5;

FIG. 9 is a perspective view of the smart clamp of FIG. 5 showingcontents of the electronics housing and various sensors in accordancewith an illustrative embodiment of the present invention;

FIG. 10 shows various components of a smart clamp constructed inaccordance with an illustrative embodiment of the present invention;

FIGS. 11a and 11b are, respectively, a top view and a side view of anelectronics housing for a smart clamp in accordance with an illustrativeembodiment of the present invention;

FIG. 12 is a perspective view of a main board of a smart clamp inaccordance with an illustrative embodiment of the present invention;

FIGS. 13a and 13b illustrate a communication network comprising dataacquisition devices (e.g., several of the smart clamp in FIG. 5) inradio communication in accordance with an illustrative embodiment of thepresent invention;

FIG. 14 illustrates a more complex example of a communication networkthan that shown in FIG. 13a or 13 b;

FIG. 15 illustrates a communication network with more than one adaptorin accordance with an illustrative embodiment of the present invention;and

FIGS. 16 and 17 are screen shots generated by an administrative systemin accordance with an illustrative embodiment of the present invention.

Throughout the drawings, like reference numerals will be understood torefer to like elements, features and structures.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

This description is provided to assist with a comprehensiveunderstanding of illustrative embodiments of the present inventiondescribed with reference to the accompanying drawing figures.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the illustrative embodimentsdescribed herein can be made without departing from the scope and spiritof the present invention. Also, descriptions of well-known functions andconstructions are omitted for clarity and conciseness. Likewise, certainnaming conventions, labels and terms as used in the context of thepresent disclosure are, as would be understood by skilled artisans,non-limiting and provided only for illustrative purposes to facilitateunderstanding of certain illustrative implementations of the embodimentsof the present invention.

Data Acquisition Device Overview

FIGS. 5-17 illustrate illustrative embodiments of the present inventionthat provide for a method, system and apparatus for a smart gridcomprising networked data acquisition devices that monitor transmissionlines or conductors. The smart grid is illustrated using powertransmission lines; however, it is to be understood that the dataacquisition devices can be configured to monitor other types oftransmission lines or conductors deployed over extensive geographicdistances (e.g., a communications line, a gas line, a water line, an oilline, a railroad, a highway, among others), and need not be restrictedto use only with connectors or clamps, in accordance with illustrativeembodiments of the present invention. A data acquisition device isillustrated using a suspension clamp (e.g., on a power transmissionline) that is hereinafter referred to as a “smart clamp.” Dataacquisition devices, however, are understood to be any related smartconnectors or smart accessories or devices for data acquisition andnetworked monitoring.

With reference to FIGS. 5-9, a smart clamp 1 is illustrated in FIG. 5.The smart clamp assembly includes a clamp body 110, a keeper body 310resting on the clamp body 110, an electronics housing 50, and a heatshield 70 that protects the electronic components in the electronicshousing 50. Also depicted are illustrative clamp hanger hardware 20 foraffixing the clamp 1 to a power line or other conductor 30, for example,and a high temperature cable 80 to connect a power source (e.g., a powersupply comprising a current transformer 330) to the electronics in theelectronics housing 50 as described below.

As illustrated in FIGS. 5, 6 and 7, the clamp body 110 includes acentral trough or channel 112 along its length on to which a powerline/wire 30 is to be placed. The keeper body 310 likewise includes acentral trough or channel 312 along its longitudinal length toaccommodate the power line 30 such that, when the keeper body 310 andthe clamp body 110 are attached, the power line 30 is secured betweenthe two bodies 110, 310. Illustrative hardware for securing the keeperbody 310 and the clamp body 110 to each other can include, but is notlimited to, a U-bolt 210 inserted into bolt holes 214 and secured vianuts 216. A similar configuration of two bolts holes 214 and nuts 216for a U-bolt 210 can be provided on opposite ends of the clamp 1.

The keeper body 310 includes a cooling chimney 111 as shown in FIGS. 5and 6 to allow air to circulate and cool the smart clamp 1. The keeperbody assembly comprises the keeper body 310, springs 320 and an upperportion 331 of the transformer 330. Similarly, as shown in FIG. 7, theclamp body 110 also includes a cooling chimney 111 that also facilitatesair circulation to cool the smart clamp 1. Accordingly, the clamp bodyassembly comprises the clamp body 110 and lower portion 332 of thetransformer 330. The upper and lower portions 331 and 332 of thetransformer 330 in the power supply can be provided with troughs orchannels similar to the channel 112 in the clamp body (e.g., asillustrated in the lower portion 332 of the transformer depicted in FIG.7) to accommodate a conductor 30, and are positioned and secured intheir respective keeper body 310 and clamp body 110 so as to be alignedto one another. When the clamp body 110 and the keeper body 310 aresecured together, the springs 320 are loaded or compressed by the upperand lower portions of the transformer 330. The spring fitting of thecurrent transformer 330 to the keeper body 310 allows for floating theconductor 30 within ranges to avoid over pressing the conductor yetprovide good seal and minimize vibrations. While the illustratedembodiments depict the power supply assembly with current transformer330 having portions 331 and 332 provided within the keeper body 310 andclamp body 110, respectively, it is to be understood that the currenttransformer 330 can be deployed in another location relative to theclamp 1. For example, portions 331 and 332 of the transformer 330 can beattached to the conductor via a clamp at a location adjacent to theclamp 1. The underside of the clamp body 110 is shown in FIG. 8 andprovides another view of the high temperature conductor 80 extendingfrom the power supply comprising the current transformer 330 towardelectronics housing 50. The power supply comprises an electronicscircuit board (not shown) configured to condition AC voltage from thecurrent transformer 330 and convert it to DC voltage to be supplied tothe main electronics board 500 via the cable 80.

Power for the Data Acquisition Device and Resolution of Thermal Issues

While it does not seem reasonable, conventional systems have difficultygetting a few watts of power (e.g., for powering a processor or sensors)from a power line carrying a million watts of power. The presentinvention overcomes these difficulties, that is, the smart clamp 1 isable to extract a small amount of power from a power line or wire 30 towhich it is secured in accordance with an illustrative embodiment of thepresent invention.

A practical means to extract power from the power line is a currenttransformer; however, to accommodate a 3 amps (A) to 3000 A conductor 30current range, this transformer becomes a substantial piece of iron(e.g., about 4 pounds) with copper windings (e.g., about 9000 turns)which extracts power from the magnetic fields surrounding the mainconductor 30 created by the electron flow therein. For example, aconventional split, square current transformer can be used (e.g., amodel CTS-1250-300A current transformer available from ContinentalControl Systems LLC, Boulder, Colo.). One side can be removed to permitclamping the transformer 330 over the conductor 30. The extracted poweris utilized to power the smart clamp 1 and its various sensors, dataanalysis components and communication equipment, which can consume asmany as 10 watts. Alternatively to extracted power (e.g., via a powersupply assembly with current transformer 330), batteries and solar cellscan also be used to power the clamp 1 electronics, among other powersources for electronics.

As stated above, the smart clamp 1 uses the power supply assembly withcurrent transformer 330 to extract power from the magnetic fieldgenerated by the current passing through the main conductor 30 to whichthe current transformer 330 surrounds. The transformer 330 can be asplit transformer having an upper portion 331 and a lower portion 332 sothat can be clamped around the power line or wire 30 as described belowin connection with FIGS. 6, 7 and 8. As stated above, a high temperaturewire 80 extends from an output of the power supply assembly to an inputof the electronics housing 50 to provide power to the electroniccircuits therein. An energy storage device can optionally be provided inthe smart clamp 1 (e.g., a capacitor on the main board 500 as shown inFIGS. 9 and 12) to allow the smart clamp 1 to operate long enough tosend a last message (e.g., to a base station or other network monitoringdevice) before power is lost.

The conductor 30 enclosed by the clamp body 110 and keeper body 310 canget quite warm due to the very large current carried by the conductor.Typically, older style wire is allowed to get to about 75° C. before itgets soft and starts to sag. Newer style wire is starting to be deployedwhich can reach 250° C. before it gets soft and starts to sag.Electronics generally will not tolerate this temperature, and thereforethe electronics housing 50 is positioned to the side and separated fromthe main body of the smart clamp by a heat shield 70. The heat shield 70can be connected to the side of the clamp 1 (e.g., with separators 72for thermal insulation) and the electronics housing 50 can be connectedto the heat shield 70, for example. The heat shield is constructed ofaluminum. The electronics housing 50 can be made of non-metallicmaterial to facilitate operation of the radio 540 and GPS unit 510.

The current transformer 330 surrounds the main conductor in order toharvest the energy, and, in some implementations, the currenttransformer 330 will not tolerate temperatures above 85° C. The holes orcooling chimneys 111 in the keeper body 310 and the clamp body 110 ofthe smart clamp 1 allow air flow to cool the transformer 330.Alternatively, as stated above, the power supply assembly with portions331 and 332 of the transformer 330 can be attached to the conductor 30via a clamp at a location adjacent to the clamp 1. Further, the smartclamp 1 itself acts as a heat sink to reduce the temperature. Thetransformer 330 can be encased in thermal insulation material to provideadditional protection.

Data Acquisition Device Sensors and Electronic Components

The smart clamp 1 includes various sensors in or near the electronicshousing 50, which is insulated from heat by the heat shield 70 asdescribed above.

With reference to FIG. 9, the electronics housing 50 is shown with acover removed to expose a main board 500 mounted inside in accordancewith an illustrative embodiment of the present invention. As shown inFIG. 5, the electronics housing 50 has a section 52 extending from amain section 51. Parallel housing sections 54 are connected to oppositesides of the section 52 and extend oppositely to each other and parallelto the longitudinal axis of the conductor 30 and clamp 1. The main board500 is secured in the section 51. Additional sensor circuits formeasuring wind speed and ambient temperature (e.g., indicated generallyat 610 and 620 in FIG. 9 and shown in FIGS. 11a and 12) are electricallyconnected to the main board 500 (e.g., via ribbon cable) and extendtherefrom for deployment in the parallel sections 54 as described infurther detail below.

With continued reference to FIG. 9, the main board 500 supports andprocesses inputs from a number of sensors and measurement devicesincluding, but not limited to, a Global Positioning Device (GPS) 510, asensor 520 for measuring conductor 30 temperature, a conductor 30current sensor 530, the wind speed detector 610, a vibration detector630, an audio corona detector 640, the ambient temperature sensor 620,and at least one camera 550 and its interface 504. Additional sensors,such as additional cameras can be included. The sensors are described inmore detail below. In addition, the main board 500 supports an encryptedradio 540 and encrypted web access 560. These communications devices aredescribed in more detail below. The main board 500 comprises a centralprocessing unit (CPU) 505 and associated memory device 502 (e.g., anon-volatile memory such as a flash disk) and program code forprocessing data from the sensors and communications. In anotherimplementation, the electronic circuitry may be located outside of theclamp or transmission line in an external box which may or may not havea faraday cage. This arrangement would be suitable, for example, for agas pipeline as well as for certain electrical transmission lines.

As shown in FIG. 11a , the electronics housing 50 can also be providedwith connectors 501 and 508 for power and fiber optics, respectively. Asshown in FIG. 12, a connector 501 is electronically connected to a powersubsystem on the main board 500 such that, when the high temperaturecable 80 carrying DC power is connected to the connector 508, the mainboard 500 can provide power to the sensors and other electronic devicesthat it supports.

FIGS. 11a and 12 illustrate a main board 500 and other components inaccordance with illustrative embodiments of the present invention. FIG.11a is a front view of a main board 500 in an electronics housing 50.The main board can be connected to a camera 550 having a lens installedin an aperture provided in the electronics housing 50 as shown on oneside of the housing 50 depicted in FIG. 11b . The other side (not shown)of the housing 50 and main board 500 can also be installed with anothercamera (i.e., with lens mounted in an aperture of the housing 50) toenable images to be taken along the sections of the conductor 30extending from both sides of the clamp 1.

An illustrative small camera 550 operates in the −40° C. to +85° C.range, and with fixed focus down to two feet, for example. The head is 8mm×5.6 mm. The camera(s) 550 can capture still images of line 30conditions such as ice, sagging, carbonized debris and so on. Videoimages can also be provided as communication bandwidth permits. Asdescribed below, by representing each smart clamp 1 with its own webpage, the respective web pages for smart clamps can present users withconvenient information regarding various line conditions such as imagesof ice and the like, and listings of measured parameters such astemperature, wind, among others and whether they are in selected rangesor not or meet selected thresholds.

There is no practical means that is cost-effective to sense voltagedirectly from the power line 30, at the present time, without relianceupon a ground-based system. While current can be sensed by a secondcurrent transformer, a Hall Effect sensor integrated circuit (IC) 530,which is smaller and less expensive, can be utilized in the smart clamp1 (e.g., on the main board 500). The current sensor 530 can be based onthe Hall Effect rather than the more traditional Rogowski coil, whereinharmonic distortion of the current sine wave is measured by a distortionthat can be caused by unusual loads, a saturated transformer, or amalfunctioning generator.

Conductor temperature can also be measured with an IC. For example, thesmart clamp 1 can be provided with a thermal jumper 520 between theconductor or transmission line to an electronic component on the mainboard 500 that can empirically determine the temperature of thetransmission line.

The smart clamp 1 can include detectors 610, 620 and 630 for measuringwind speed sensor, ambient temperature and conductor vibration,respectively, as illustrated in FIG. 9. The wind speed detector 610 isadvantageous because it is implemented with no moving parts. Inaccordance with an embodiment of the present invention, wind speed issensed by a heated element extended from the body of the clamp 1. Forexample, two wind detection devices are disposed proximally to theelectronics housing 50 and on the same axis as the conductor ortransmission line 30 coupled to the smart clamp 1. The differencebetween the temperature of the element predicted in still air and thetemperature drop in the other element caused by wind can be used tocalculate wind speed.

More specifically, as stated above, the electronics housing 50 hasparallel housing sections 54 which extend parallel to the longitudinalaxis of the conductor 30 and clamp 1 and in which the detectors 610 and620 for measuring wind speed and ambient temperature are deployed. Asshown in FIGS. 11a and 12, a main board 500 can have a main section 506and at least one section 507 extending therefrom (e.g., via ribbon cableor other conductor). The section 507 supports at least the wind sensor610 and the ambient temperature sensor. The wind speed detector 610operates generally using the same principle as a hot wire anemometer inthat it comprises one of the parallel sections 54 (e.g., see “503 a” inFIGS. 11a and 12), which is heated by an element (not shown). As windblows over the clamp 1 including the parallel sections 54, the heatedsection 503 a cools. The other section 54 (e.g., see “503 b” in FIGS.11a and 12) is provided with the ambient temperature sensor 620. The CPU505 is programmed to determine wind speed based on the differencebetween the measured ambient temperature and the measured temperature ofthe heated section 503 a. The ambient temperature sensor 620 is placedin the section 503 b opposite from the heated section 503 a so that itsmeasurement of ambient temperature is not skewed by the heating elementfor the heated section 503 a. The CPU 505 can be programmed to determinewind speed in the direction perpendicular to the longitudinal axis ofthe conductor 30 (i.e., a parameter often sought by utility companies)using various geometrically-based calculations.

It is to be understood that the wind speed detector 610 can beimplemented using other configurations in accordance with otherillustrative embodiments of the present invention than that shown inFIGS. 9, 11 and 12. For example, as shown in FIG. 10, a clamp 1 can beprovided with a protrusion from its housing 50 to accommodate a hot wireanemometer 612, and optionally a radio antenna 542 for a radio interface540 described below.

The vibration sensor 630 can be implemented a number of different ways.For example, a tension meter with adequate bandwidth (128 Hz) can beused to measure vibration. If a relatively large tension meter is notpresent, then a smaller, 3-axis accelerometer can be installed 1 or 2feet away from the clamp 1, or a similar device can be integrated intothe smart clamp 1 itself. If an external sensor is used, movement can bemeasured and provided to the main clamp 1 via four wires (i.e., two forpower and two for communication), for example, for interfacing to theboard 500 and its CPU 505.

More specifically, measuring tension in a wire conductor 30 cangenerally be performed using a device (e.g., a Quick Balance tensionmeter available from Dillon, an Avery Weigh-Tronix company in Fairmont,Minn., that is installed in or near the clamp 1 and clamped onto theconductor 30) which deflects the wire 30 a little and measures the forcethe wire exerts in an attempt to be straight. The CPU 505 can usegeometric-based calculations to provide a scaling factor between theforce on the device and the tension in the wire 30. Measuring tensioncan also be performed using an external sensor such as a load cell witha mechanical disadvantage to bring the 10,000 lb. max tension to 100-200lbs., as shown in FIG. 10, which can be sensed. Vibration can also besensed by sensing variation in tension or measured with an accelerometerIC attached to the line a short distance from the clamp 1.

As stated above, the clamp 1 also has a corona detector 640. Corona oninsulators is not in the visible spectrum. It is in deep ultra violetspectrum (e.g., about 280 nm). Cameras that can take images of ultraviolet flashes are prohibitively expensive, particularly when it istaken into account that corona is sporadic, intermittent andsignificantly affected by air pressure, moisture and other dynamicconditions. Silicon sensors are not very sensitive to this range, thatis, they are about 10% efficient as compared to sensitivity to visiblelight. A very good filter is required to remove visible light, even atnight. During the day, the sensor would be swamped with visible lighteven with the filter. Visible light cameras in general do not survivethe temperature extremes of the environment of the monitored line 30,even if the cameras are turned off. In accordance with an illustrativeembodiment of the present invention, a method of corona detection isprovided that employs audio corona detection (e.g., storing an audiosignature(s) of corona and employing sensors for detecting audio noiseand performing comparisons with signature(s) to detect corona). Theaudio-detected corona can be time tagged and its duration recorded,among other parameters.

With continued reference to FIG. 9, the audio corona detector 640 cancomprise a microphone and digital signal processor (DSP) (not shown) toobtain and process an audio signature (“sizzling sound”) of corona.Samples of frequency sampled corona sounds can be stored as signatures.The output of the microphone can be continually or periodically sampledby the DSP. The DSP then compares the samples to signatures or otherwiseprocesses samples with respect to selected threshold characteristics todetermine if an alert should be generated that a corona event hasoccurred. An alert can be sent, for example, each time a corona event isdetected, or after a selected number of detected corona events hasoccurred to assist with calibrating the DSP to more accuratelycharacterize sounds as corona events.

One or more smart clamps 1 may detect a lightning event. The smart clampsystem utilizes a GPS unit 510 to precisely locate the positions of thesmart clamps 1. Using GPS also allows for the measurement of the precisetime information for measuring one or more events sensed or detected bythe smart clamps 1 (e.g., phase angle). An antenna is provided on themain board 500. A 300 kHz bandwidth filter is also provided to detectsurges from a lightning strike. It is not necessary for lightning tostrike the line to detect the lightning. For instance, lightning strikeswithin a few miles from a smart clamp can be detected and time stamped.Geometry shared among three collocated smart clamps 1 allows fortriangulation of the strike location.

In addition, the smart clamp 1 can be configured to take voltagemeasurement of the power line. At present, it is very expensive tomeasure 110 kv to 765 kv, which is typical for a power transmissionline. Regardless, voltage with respect to the ground could be measuredusing an external voltage detector which communicates over the sameradio links (not shown).

In accordance with an illustrative embodiment of the present invention,a short range (e.g., 2 km) radio network can be used in the smart gridsystem whereby the smart clamps 1 or other data acquisition devices can“hop” data along the transmission line 30 until aggregated data can bebrought to a remote terminal, which could interface to public or privateland based transmission as described in connection with FIGS. 13-15.

With reference to FIG. 9, a clamp 1 is provided with a radio (e.g., anencrypted radio) 540. For example, the radio 540 can be a standard, FCCapproved, digital radio with a data rate of 250 kbps, and AES128encryption, which is low cost, environmentally robust and also savesdevelopment cost and minimizes deployment cost. One such radio is aSynapse RF Engine ZigBee Radio Board (RFET) available from SynapseWireless Inc., Huntsville, Ala. Having dimensions of approximately 1.33″per side, it can be provided on the main board 500 in the electronicshousing 50, as shown in FIGS. 9 and 12. With a 5″ antenna, as shown inFIG. 11a , the radio 540 has a range of approximately 2-3 km.

To interface to public or private land based transmission, an optionalillustrative optical interface 600 can be provided to a data acquisitiondevice main board 500 that operates as standard 100BaseFX Ethernet 100Mbps Media Independent Interface (MII) to the main processor on theboard 500 in accordance with an illustrative embodiment of the presentinvention.

FIGS. 10 and 11 a depict an optional optical interface 600 installed onthe main board 500 in accordance with another illustrative embodiment ofthe present invention. The optical cables 602 can be provided withstrain relief. Optical splitter/combiners are indicated generally at604. The optical interface 600 can comprise a dual small-form factorpluggable (SFP) to support linear fiber drop and continue topology.

An optical connector 606 (e.g., a weather tight fiber optic connector)can be provided in the electronics housing 50, in addition to aconnector 508 for the power cable 80. The optical interface 600 isuseful at ground level or in applications or in lower voltageapplications when the optical cable will not shunt the effect of highvoltage insulators. Alternately, the main board 500 can be reused as aradio-to-Ethernet adaptor 710 at certain sites and include, forconvenience, a standard RJ45 electrical 10/100BaseT interface as well asor in lieu of the 100BaseFX optical interface.

The low power radio 540 in each of the smart clamps 1 in the smart clampsystem includes powerful encryption and is used to communicate back to acentral location 700, as will be described in connection with FIGS.13-15. For a long power transmission line 30, there could be hundreds ofsmart clamps 1 and, therefore, hundreds of radio hops that would berequired to reach a switching node 700. Illustrative embodiments of thepresent invention implement encryption and large numbers of hops betweendata acquisition devices over long distances and therefore accommodatethe transmission delays that remain a problem for existing radiotechnology.

For ease of use and in accordance with an advantageous, illustrativeembodiment of the present invention, the smart clamp system can requirelittle or no knowledge of communication protocols, radio technology, orother technologies that are not presently familiar to power companiesthat would use the smart clamp system. As long as clamps 1 are installedwithin their radio range, they will communicate with the main computersystem (e.g., a central monitoring location 700) upon installation. Onceinstalled, the clamp 1 begins to operate automatically. Power isautomatically provided to the electronics 500, sensors automaticallybegin to detect real-time conditions, the GPS 510 determines the clamplocation, the radio 540 detects neighboring clamps and substationadaptors 710, and communications begin. This embodiment is thereforesuperior to existing technology that requires programming a centraldatabase to organize remote sensing devices or the need to program inindividual nodes with cell phone numbers or IP addresses to administer asensor network.

In accordance with an illustrative embodiment of the present invention,each smart clamp 1 is configured to operate as an internet web server.The communication can be set up over a private network, so there is noconnection to the public Internet, to improve security. The smart clamp1 can include an encrypted web access unit 560 to enable secure accessto the Internet, as shown in FIG. 9, for e-mail alerts and tosurf-the-grid (i.e., browse web pages created for each clamp 1 to obtainmeasured parameters and other information).

When a fault is detected, the smart clamp 1 is configured (e.g., viafirmware provided to the CPU 505) to send a message (e.g., in the formof an e-mail) to a programmable address with a short message to indicatethe problem and the location. One arrangement can include measures tolimit or coordinate the number of such messages to minimize“overloading” a central monitoring point 700. The messages are thencommunicated via a radio communication link to an adaptor 710, forexample, for aggregation and optionally to other ground based monitoringstations 700 (e.g., via ground based communications) if not co-locatedwith the adaptor 710.

The radios 540 used by the smart clamps 1 can be adapted to standardEthernet quite easily and tied to an ordinary local area network. A useris able to access the smart clamp devices 1 by entering respective webpage addresses and thereby searching or querying the grid. It is notedthat conventional monitoring systems require a highly specialized andvery expensive central computer system and software to gather themeasurements. The simplicity of expanding the system and ability to beaccessed from many sites can be well established, and the system can beeasily implemented by using inexpensive Ethernet equipment that isreadily available.

Radio Issues

At present, the Zigbee radio is a standard, packet-based, low powerradio intended for providing communication within a building or overonly a few acres. However, it does include AES128 encryption which iscurrently considered effective. However, in 5 years, such encryption maybe considered to be inadequate. It is noted that all Zigbee radios in anetwork must use the same encryption key. If the key changes, all radiosmust be updated at the same time. For about 20 radios on one property,that may be considered to be acceptable; however, for tens of thousandsof radios spread across an electric grid or other network of dataacquisition devices as proposed in accordance with embodiments of thepresent invention, using conventional Zigbee radios in a network wouldnot be a good system. For example, breaking only one encryption keywould make the entire system vulnerable. In addition, the Zigbeestandard sets a limit on the response delay that is reasonable for 10 or20 radio hops, but it cannot accommodate, for example, 500 hops, asneeded for a power transmission line application or other geographicallyexpansive application contemplated by illustrative embodiments of thepresent invention.

The Zigbee standard describes two kinds of radios: a coordinator and aperipheral. Coordinators are responsible for repeating messages to getthem to the desired destination if a repeat is needed. The provision ofa radio as either coordinator or peripheral is a manual setup operationthat needs to be avoided based upon the potential deployment of tens ofthousands of smart clamps 1. In accordance with the illustrativeembodiments of the present invention, for simplicity and ease of use, atechnician can install the clamp 1 with a ratchet wrench and completethe installation without knowing anything about communication protocolsor network architecture.

Radio Protocol for Very Large Networks

While conventional Zigbee radio may be an adequate starting point for asimple radio design, it is inadequate for geographically expansiveapplications such as those accommodated by illustrative embodiments ofthe present invention. An illustrative embodiment of the presentinvention provides a customized Zigbee radio design that institutesadvantageous changes for use with the smart clamp 1 in a smart clampsystem. Instead of having one encryption key for all radios 540 in thesystem, for improved security, the keys are dynamically provided (e.g.,negotiated at each transaction in a manner similar to how internet banktransactions are handled). For example, it can be implemented in theSecure Socket Layer (SSL) which is part of all web browsers. Inaddition, the tolerance for delay is extended substantially. Instead ofa few milliseconds, replies on very long lines could take a minute. Ifan Ethernet port that consists of smart clamp electronics 500 with botha radio 540 and optical or electrical Ethernet interface 600 can beinstalled at the base of a tower in the middle of long line, the datacan be backhauled over leased telecom lines or private lines owned bythe power company. This reduces the maximum number of hops and reducesthe response delay. However, smart clamp communications message routingis uniquely designed to be tolerant of the described very long delays tosupport large networks even if leased telecom lines or private lines arenot available.

Each smart clamp 1 is configured (e.g., via the programmed CPU 505, theradio 540 and other devices on the main board 500) to implement messagerouting similar to a common Ethernet switch. Some of the same conceptsare used, but substantial modification is provided in accordance withillustrative embodiments of the present invention to accommodate theradio environment as described below.

The smart clamps 1 in accordance with illustrative embodiments of thepresent invention are intended to be installed, with a life expectancyof approximately 20 years or longer. It is noted that telecom equipmentthat lasts a similar period, in an outside environment, is currentlyavailable. As an alternative to using radios 540, smart clamps 1 can beprovided with lasers for optical communication, but their lifeexpectancy may be limited to 5 to 7 years, which is far shorter than theradio equipment 540. At ground level, where smart clamps 1 having both aradio 540 and optical or electrical Ethernet interface 600 can be usedto communicate over a conventional utility or telephone company circuit,an optical interface 600 is easily serviced if it becomes necessary.

While the smart clamp 1 hardware can last as long as 20 years, thesoftware, encryption, communication protocol, and other features of asmart clamp 1 are likely to become obsolete over that time period. Thesmart clamp 1, however, includes data storage that operates like a diskdrive (e.g., flash drive 502). Software can therefore be updatedremotely to accommodate most of these changes or updates.

When future requirements simply outstrip the capability of the existinghardware, new electronics can be installed without removing the entireclamp. The side box or electronics housing 50 containing the electronicscan be replaced separately. This is also an important factor forreplacing failed or malfunctioning smart clamps 1.

As stated above, implementing a radio network for a geographicallyexpansive transmission line grid (e.g., a power transmission grid)presents challenges that are not present in a smaller geographic area.Transmission lines 30 are inherently linear covering extremely longdistances—up to 500 miles or longer. In as much as highways are oftenmonitored mile by mile, it is desirable to monitor transmission lines atleast every mile to help pinpoint issues and characterize performance.While there are cost-effective unlicensed radios with a nominal 1 milerange, sending a message via such radios from one end of a 500 miletransmission line to the other could require 500 radio repeats in eachdirection which requires a communication protocol that can accommodatevery long delays. That is, the maximum response time (before the messageis deemed lost) would necessarily be minutes instead of milliseconds.

The long transmission line 30 is not the only issue. The network formonitoring smart clamps 1 also branches when several radios 540 are inclose proximity (e.g., when smart clamps 1 are installed to monitor all3 phases on one tower or when several transmission lines 30 converge ata substation). All of the smart clamps 1 need to be able to assembleinto a coherent communication network without manual intervention inaccordance with an advantage of an illustrative embodiment of thepresent invention.

In accordance with an illustrative embodiment of the present invention,a more practical network is achieved by adapting the smart grid to amore common media and protocol stack such as Ethernet and TCP/IP. Thus,a radio-to-copper or optical Ethernet adaptor 710 is placedstrategically around the power grid, for example. Certainly, substationsare a likely place for such an adaptor, but there could be convenientpoints along a transmission line 30 for an adaptor as well. The adaptor710 comprises a radio 540, a standard Ethernet port 712, and suitableprotocol conversion. The resulting Ethernet interface is thereforesuitable to interface with public communication lines (telcos), privatenetworks, cable TV modems, DSL, and/or other internet type accesstechnologies.

As stated above, a main board 500 can be used as a radio-to-Ethernetadaptor 710 at certain sites. An example of a data acquisition devicemain board that can be configured as an adaptor 710 is provided in FIGS.10 and 11 a. The adaptor 710 can be physically different from the linedata acquisition device (e.g., a smart clamp 1) and has a differentfunction. The adaptor 710 can identify itself as a port where messagesoriginate and are terminated. It is a homing location. An illustrativeoperation of the data acquisition devices (e.g., smart clamps 1) and thenetwork organization is to reach one of these adaptors 710 with minimaldelay which is defined as the minimum number of repeats or hopsrequired.

When a packet is received by a data acquisition device (e.g., a smartclamp 1), there are three options for disposition of the message, by wayof an example. If the message is intended for the same data acquisitiondevice, the CPU 505 of the data acquisition device processes themessage. If the message is not intended for this local data acquisitiondevice, either the message is repeated, or it is not repeated because itwill be routed by another device. Messages can be images (e.g., still orvideo images capture by the camera(s) 550), measured or sensedparameters from the data acquisition device that can be reported invarious formats, standardized messages or alerts (e.g., text, audio, orgraphics), e-mails, HTML files, among others. The messages arepacketized by the CPU 505, for example. As explained below, the messagesare aggregated (e.g., via an adaptor 710) for access by a user (e.g.,using a web browser and web address assigned to each adaptor 710).

Each message can include an 8 byte long source address and 8 bytedestination address. These addresses are the Media Access Control (MAC)address which is programmed in during manufacturing and unique to everyradio. The MAC address is used to route the packets. While a layer 3protocol, such as Internet Protocol (IP), might seem more appropriate,some manual setup (which could be time consuming, require accuraterecords and be unfamiliar to utility technicians who are bolting thesmart clamp or similar accessories in place) could be required to setthe IP address. In addition, each of the data acquisition devices 1 isbeing used as a web server in accordance with illustrative embodimentsof the present invention. This requires a fixed IP address rather thanan IP address that is assigned automatically as would be the case ifDynamic Host Control Protocol (DHCP) is used. To avoid the issue, therouting by data acquisition devices such as a smart clamp 1 is performedat layer 2, the media layer.

With each smart clamp 1 operating as a layer 2 router, each dataacquisition device or smart clamp 1 will need to track thousands of MACaddresses to know whether to repeat or not repeat a message. This is notpractical for a moderately sized CPU 505. Instead, each data acquisitiondevice can be provided with a high speed memory 502 attached to customhardware (not shown) in the main board 500 that compares a list of knownMAC addresses to that of the destination address in the packet. Uponfinding a match, the data acquisition device will know whether thepacket needs to be repeated or simply ignored.

In an illustrative implementation, the number of MAC addresses islimited to a selected number (e.g., on the order of 26,400) that is acompromise of processing speed, packet duration time, and powerconsumption while still maintaining the requirement of thousands ofdevices in a single subnetwork. If required, larger numbers of MACaddresses can be supported.

To create the table of MAC addresses in the high speed memory 502, eachdata acquisition device needs to announce it is present. In the simplestcase, this is begun with a broadcast message from an adaptor 710. Eachdata acquisition device (e.g., smart clamp 1) forwards the message butincrements the hop count within the message. Each device also replies tothe message with the minimum hop count received. Naturally, each device1 will see many copies of the message. In most cases, the earliestmessage will have the smallest hop count, and the device will reply withthat hop count. However, there are some less likely situations where asmaller hop count can be received later in the process. The device willreply to this smaller hop count which appears later. However, it willnot reply to the adaptor 710 with a larger hop count.

During this process, each data acquisition device (e.g., smart clamp 1)will become familiar with devices in the immediate vicinity. Each devicewill know the hop count to the adaptor 710 for its neighbors. Ingeneral, the devices with the lowest hop count will be responsible forperforming repeat operations for devices with higher hop counts.However, each device is configured to perform a repeat or hop even whenit appears there is a lower count path available.

Consider a simple linear case, as shown in FIGS. 13a and 13b . Dataacquisition device #1 will be 1 hop count from the adaptor 710. Dataacquisition device #2 will be 2 hop counts since device #2 is not inrange of direct connection to the adaptor 710. Device #3 is 3 hop countsfrom the adaptor.

The adaptor 710 issues the configuration broadcast. Device #1 repeats itwith a hop count of one. It also replies to the adaptor 710 with a hopcount of 1. Device #2 will receive the repeated configuration messagewith a hop count of 1 and the reply from Device #1 with a hop countof 1. Device #1 will take the reply from Device #2 and repeat it to theadaptor 710 with an incremented hop count. Device #2 repeats theconfiguration message with a hop count of 2 and also replies toward theadaptor 710 with a hop count of 2. Device #3 receives the repeatedbroadcast from the adaptor 710 and replies to it with an incremented hopcount. Device #2 repeats the reply from Device #3 toward the adaptor 710with an incremented hop count.

Device #1 determines that it can communicate directly to the adaptor710. It also determines that the Device #2 reply did not have a hopcount of zero, and so Device #2 must be relying on Device #1 tocommunicate to the adaptor 1. Device #1 also determines from themessages that another device is in the network (i.e., Device #3) and hasan even larger hop count. Accordingly, Device #1 repeats messages to theadaptor 710 from that device as well.

In a more complex situation, there are multiple valid paths back to theadaptor as shown in FIG. 14. This example assumes all 3 phases of apower transmission line 30 are being measured at the same points.

In this case, all A devices (e.g., Devices A1, A2, A3) can receivemessages from each other and all B devices (e.g., Devices B1, B2, B3)and the adaptor 710. All B devices can hear all A, B, and C devices(e.g., Devices A1, A2, A3, B1, B2, B3, C1, C2 and C3), but not theadaptor. All C devices (Devices C1, C2 and C3) can hear B devices and Cdevices. The decision on the path is not longer but rather just a matterof the only path available. A decision factor in this case will be theMAC address. For example, the device with the lowest MAC address will bethe repeater. While the MAC address is 8 bytes long, manageably shortnumbers are used in this example. Device B1 will have address 10, B2 is11, and B3 is 12. Devices B2 and B3 will be able to receive the responseof Device B1 and realize the number of hops provided back to the adaptor510 is the same as the number of hops they are providing. The MACaddress of Device B1 is the lowest so Device B2 and Device B3 willautomatically defer to allow Device B1 to perform repeats for DevicesC1, C2, and C3. The use of the lowest MAC address is arbitrary. Thedecision can be made by using some other fixed relationship between theMAC address such as choosing the highest address or other factor.

In the above example, any one of the devices could fail and there wouldstill be a path back to the adaptor 710 at the left side. Somereconfiguration could be required. For that reason, the reconfigurationmessage is periodically broadcast from the adaptor 710 (e.g., every 15minutes). If a device realizes it can no longer communicate with theadaptor 710, it can issue a request to reconfigure which all deviceswill repeat toward the adaptor 710.

A network, as shown in FIG. 15, can have more than one adaptor 710. Forexample, another adaptor can be representative of a transmission line 30between two substations where there is an adaptor at each substation.

Assume Device A1 has the lowest MAC address among Devices A1, A2, andA3. Device B1 has the lowest MAC address among Devices B1, B2, and B3.Device C1 has the lowest MAC addresses among Devices C1, C2, and C3. Theshortest number of hops to an adaptor for the A devices is to the left.The shortest path to an adaptor for the C devices is to the rightadaptor. The B devices could reach either adaptor with 2 hops. The tiebreaker will be the MAC address of Device A1 and Device C1. The Bdevices will use the path with the lowest MAC address of either DeviceA1 or Device C1.

A system with three or more adaptors can be accommodated with the samealgorithm. First, find the closest adaptor in terms of the number ofhops. Where there is a tie, use the MAC address of the nearest repeatersto break the tie.

With continued reference to FIGS. 13a and 3b , an adaptor 710 can bemounted outside on a wall or a pole and be within, preferably, line ofsight of a clamp 1. The adaptor 710 can be provided with a standard RJ4510/100BT electrical Ethernet connection for ground-based networkconnections, and use 90 VAC to 264 VAC, 50 Hz or 60 Hz power andapproximately 2 W. Other power connections, such as −48 Vdc, may beused. If a telco provides only a T1 (often called DS1) or E1 connection,standard Ethernet-to-T1 or E1 adaptors may be used to convert theadaptor 710 Ethernet signal to the telco T1 or E1 interface to establisha T1 or E1 private line from the adaptor site to the remote surveillancelocation 700. If neither a T1 or E1 private line nor a fully privatenetwork is used for the circuit between the adaptor 710 and the remotesurveillance location or central station 700, a VPN network can be usedto assure restricted access. The adaptor 710 includes sophisticatedencryption to further address security concerns. In FIG. 13b , the handoff from the intermediate utility to the telco VPN can be T1, E1, DSL,cable modem, microwave hop to another site, among other methods. If theadapted connects the grid or network to a remote surveillance point orcentral station 700 by the internet, a gateway, firewall and VPNconnection can be used for security reasons.

Each clamp 1 adaptor 710 has an integral web page server 560. One IPaddress is assigned at the remove surveillance point or central station700 for each adaptor 710. For example, only one IP address need beassigned per adaptor 710, while an IP address for each clamp 1 does notneed to be assigned. This IP address is programmed into the one or twoadaptors 710 in a network. The adaptors 710 then automatically discoverboth the remote surveillance point or central station connection and allclamps 1 in the network as described above.

Surveillance personnel can then be provided with a browser address foraccessing the remote adaptor 710. Once the browser address is entered, aprivate web page appears that provides access to the data from eachclamp 1, longitude and latitude for each clamp which may be linked to amap, means to re-name clamps (Route 43 and Highway 22, for example),means to set thresholds (vibration, temperature etc.), and means toenter e-mail addresses that should be used to notify specific personnelif thresholds are crossed. The addresses can be clamp-specific in casethe transmission lines span several maintenance regions. The number ofe-mail alerts that are sent can be limited.

Thus, in accordance with an illustrative embodiment of the presentinvention, an administrative system is provided to facilitate monitoringand processing the collected data received from various data acquisitiondevices (e.g., a clamp 1). The administrative system can be implementedin processing devices used to aggregate and analyze the collected datasuch as an adaptor 710, central monitoring point 700, or a computingdevice with internet connectivity provided at a base station(s) or otherlocations. The administration system can use screens or web pages andweb servers, which can be built-in. Firmware is provided to the dataacquisition devices. Thus, no external software is needed.

FIGS. 16 and 17 are illustrative web pages generated via theadministrative system. A user (e.g., monitoring network administrator)is provided with an assigned Internet Protocol (IP) address with whichto type into a web browser (e.g., Internet Explorer, Foxfire and thelike) to navigate to the home page shown in FIG. 16. The home pageprovides a number of options for managing individual data acquisitiondevices and network(s) of data acquisition devices, that is, byselecting one of the options, a user can view system conditions as wellas provision their device(s) and/or network(s). In the illustratedembodiment, the data acquisition devices are clamps 1 and referred to asData Acquisition Suspension Clamps (DASCs). The IP address can beassigned to a base station, for example. A base station can be providedfor each isolated network. By way of an example, selecting the DASC Listoption causes a screen or web page (not shown) to be provided to theuser that lists DASCs by device identifiers. The user can then selectone of the listed DASCs to navigate to a data page for that DASC asshown in FIG. 17.

With reference to FIG. 17, the data page indicates parameters for theselected DASC (e.g., clamp 1) and their corresponding dates/times ormeasurement which have been communicated to an aggregating device (e.g.,adaptor 710) via the multi-hop radio communication system describedabove in connection with FIGS. 13-15. The parameters can be, but are notlimited to, maximum and minimum ambient temperatures, maximum andminimum wind speeds, maximum and minimum current, maximum and minimumvibration, and maximum and minimum wire temperatures, among others. Thedata page 17 can also indicate events such as corona events and tiltevents (e.g., number of and duration of such events as determined bydeviations from conditions at the time of installation or upon a resetcommand to a particular smart clamp) and numbers of surge and impulseevents, among others. Event history logs can be created based on thisdata, allowing a user to select the Logs option on the page depicted inFIG. 16 to view event histories.

With reference to FIG. 16, a user can select a DASC Samples option tonavigate to a page (not shown) listing a number of available datasets.For example, a user can obtain a CSV file (i.e., comma separated values)upon by selecting one of the listed items.

With continued reference to FIG. 16, by selecting the DASC Map option onthe home page, a user can be provided with a map showing the locationsof data acquisition devices within a designated geographic area. Thelocation coordinates can be collected by the administrative system andcorresponding database either dynamically using the GPS device 510provided in each of the data acquisition devices (e.g., via messaging)or pre-configured at the time the devices are installed or otherwisedeployed.

For example, the integral GPS system 510 within each clamp 1 reportsback its precise longitude and latitude. These data can be linked to,for example, utility-based mapping or, if suitable firewall and gatewaysafeguards are in place, Google maps. A typical Google map will show apushpin for each clamp 1 location, include an ability to zoom in, andusually provide an ability to retrieve stored satellite images for theterrain in the vicinity of each clamp. If there is no direct connectionbetween a smart grid network and Google maps, longitude and latitudeinformation can be entered into Google maps manually on a separatenetwork and the information used to establish a meaningful name for eachclamp 1. Alternatively, the location can be entered into a proprietarymap system already in use.

GPS positioning and DASC self-learning function can be provided in eachdata acquisition device 1 to permit DASC networks to evolveautomatically. For example, a DASC 1 can be configured to obtain itsposition information and generate a location alert to a base station 700and/or adaptor 710 at start up and/or periodically, in addition tosending parameter measurement. Thus, every new DASC 1 can beautomatically recognized by a base station 700 and/or adaptor 710 withits location automatically determined such that corresponding dataaccumulation and reporting starts immediately and automatically after aninitial deployment or restart. The administration system illustrated inconnection with FIGS. 16 and 17 is advantageous because it provides acomprehensive view of transmission line conditions to enable confidentdynamic line ratings (e.g., to help address peak and emergency demands),immediate and precise identification of line failures, proactivemaintenance, diagnosis of recurring problems. The clamps 1 themselvescommunicate with one another which permits self-learning and awarenessof long-term trends to help predictive maintenance.

By selecting an Alerts option on the home page depicted in FIG. 16, auser can access e-mail alerts that are automatically generated by thedata acquisition devices 1 and transmitted to the base station 700and/or adaptor 710 or other device implementing the administrativesystem. As stated above, data acquisition devices 1 can be configured tosend alerts (e.g., e-mail messages or other type of transmitted signalalert) when measured parameters are outside a selected range or varyfrom a selected threshold by a selected amount. The Configuration optionon the home page (FIG. 16) provides one or more pages (not shown) thatenable a user to provision device(s) and/or network(s) of devices. Forexample, configuration pages can be provided that enable setting ofparameter threshold deviations needed for automated alerts (e.g., aparameter exceeds a threshold be a selected amount or an event hasoccurred a selected number of times within a selected time period). Thedetermination of such deviations can be performed at the dataacquisition devices (e.g., via the CPU 505 on the main board 500 inaccordance with the firmware). Alternatively, the data acquisitiondevices can merely report measurements of parameters to the base stationor other monitoring location 710, 700, which instead makes thedetermination.

It is to be understood that other options and web pages are available.For example, the data page (FIG. 17) and/or home page (FIG. 16) canprovide a link or navigation option to another page or a pop-up on thesame page that provides the live camera view(s) for a selected DASC. Forexample, one or both views of the cameras in a clamp 1 (e.g., therespective views of oppositely extending sections of the monitored line30) can be provided to allow a user to make a visual assessment ofwhether sag or galloping is occurring or to otherwise assess damage to aline (e.g., icing, mechanical failure of the line or tower, and so on).Image processing can also be provided (e.g., at the base station orother monitoring station) to automatically assess images provided by thecameras (e.g., comparing different images) to determine whether certainconditions are present (e.g., sag) and to automatically generate alertsas needed.

As described above and in accordance with illustrative embodiments ofthe present invention, a clamp 1 or other data acquisition deviceconfiguration can be provided with one or more sensors for monitoringselected transmission line 30 conditions including, but not limited toambient temperature, conductor temperature, wind speed perpendicular tothe line (e.g., measurement is done without moving parts to assurelong-term quality and reliability), vibration, current amplitude,current quality (e.g., harmonic distortion), current surges, preciselocation via GPS, precise timing via the GPS, transient or surgelocation via precision time stamping and automatic clamp-to-clampcommunications, corona, tilt changes (e.g., as measured by the clamp's3-axis accelerometer), sag changes (e.g., as displayed by a pair ofintegral clamp 1 cameras that look down both directions of the line 30),galloping (e.g., as detected by the vibration sensor and seen by thecameras), local conditions (e.g., via still visual images in bothdirections of the line 30 to help detect icing or mechanical failure ofthe line or tower, internal operation via continuous self diagnosis(e.g., as programmed into the CPU 505), operating conditions ofneighboring clamps on other phases, and so on.

Thus, the data acquisition device (e.g., clamp 1) provides anunprecedented ability to integrate transmission line operatingconditions in real-time. Rather than piecemeal visibility at a singlelocation or reliance upon inferred data such as sag to estimate linetemperature, new Dynamic Line Rating capabilities and visibility aremade possible by the clamps that delivers precise mile-by-mile data thatcan be integrated and used to dynamically vary line 30 loading withconfidence. Risks associated with dependence upon a few data points canbe dramatically reduced and replaced by a Dynamic Line Rating based upon(a) precise real-time wind speed determination that automaticallymeasures the cooling effect of wind perpendicular to the line; (b)precise total current measurements made along a line 30 to uncovervarying parasitic losses and other issues that limit capacity; and (c)wide-bandwidth current measurements in real-time. Wide-bandwidth currentmeasurements reveal harmonics that waste energy and increase heating.These real-time data can then be used to optimize network operation anduncover associated stresses to components such as transformers.

As stated above, another advantage of the data acquisition device (e.g.,clamp 1) constructed in accordance with an illustrative embodiment ofthe present invention is self-powering. The clamp 1 includes an integralor associated current transformer 330 which provides all necessarypower. No batteries or connection to external power is required. Energystorage without batteries is also provided (e.g., a capacitor(s)) tosupport final messages should a line 30 fail. The clamp 1 therefore cancontinue to operate (e.g., for several seconds) to provide finalreports.

As described above, wireless communications are established between theclamps 1 and between a clamp array (e.g., as illustrated in FIGS. 13-15)and a substation or other convenient ground location 710. Data is thencommunicated over a private or public network to surveillance locations700. The multi-hop radio communications described herein in accordancewith an illustrative embodiment of the present invention provideresilient communications. Failure of a clamp 1 for any reason isdetected and reported by neighboring clamps without disruptingend-to-end communications. Further, the communications are secure.Security similar to that used for on-line banking transactions isutilized along with other measures to help assure network integrity asdescribed above in accordance with an illustrative embodiment of thepresent invention.

The integral GPS 510 provides precise timing and automatically locateseach clamp 1. An integral web browser 560 dramatically simplifies dataacquisition via web page selection of thresholds, alerting e-mailaddresses and comprehensive display (e.g., of up to 7 days ofaccumulated data).

There are several ways to utilize data collected by a network. A fewshall now be discussed for illustrative purposes.

Flexible reporting is achieved by reports and images that appear as webpages (i.e. HTML files). The basic files display collected data in aseries of tables on multiple pages. If a different presentation orappearance of the data is preferred, the system permits new HTML filesto be uploaded to each clamp. Each clamp 1 is operated independently andcan have its own unique HTML files. This may appear overly complicatedinitially, but larger arrays that span multiple transmission facilitiescan benefit from this ability to optimize the presentation of data tofit varying circumstances.

Fault or alarm conditions are immediately reported via e-mail. Eachincident can then be investigated further via the report and imagepages.

A web-based form is provided to set alarm or warning limits for variousparameters such as maximum current, current surge, maximum conductortemperature, or maximum vibration. Local conditions such as corona canbe set to trigger an e-mail or be ignored. The form also permits entryof e-mail addresses for notifications and a means to limit the number ofe-mails each clamp 1 can send in an hour.

When a fault occurs, the network can identify what the problem was andthe area where the problem occurred in accordance with illustrativeembodiments of the present invention. E-mails can be sent to firstresponders so that a team can be dispatched (or not) based uponreal-time site data. Time is saved, dispatched crews may be able tobring appropriate repair equipment, repair progress can potentially bewitnessed and the repairs can be monitored.

Illustrative embodiments of the present invention also improve uponfinding stressed or compromised facilities. Excessive temperature, tiltand other factors can lead to a failure. Knowing that lines arecompromised enables pro-active maintenance to prevent outages. Withregard to finding and monitoring vibration problems, dampers aredeployed to limit the vibration. Although real-world dampereffectiveness has been demonstrated and they work well in manyapplications, real-time effectiveness based upon wind and towerconditions can now be monitored to optimize effectiveness and uncoverunknown or suspected issues.

The illustrative embodiments of the present invention allow maximizingcapacity. Transmission facilities have conventionally been designed forworst-case conditions. In some instances, a 25% safety margin has beenused to assure resiliency. Knowing real-time wind and temperatureconditions in accordance with illustrative embodiments of the presentinvention can permit loads to be safely increased during peak periods orwhen another segment is out of service.

The illustrative embodiments of the present invention provide cascadefailure analysis. A cascade failure occurs when one element breaks andcauses several other network elements to fail unexpectedly. Fortransmission lines 30, most recorded observations are limited tomeasurements at substations or originating points. The distributedintelligence available from a smart clamp network helps theunderstanding of such a failure, what precipitated it and how toengineer improvements for existing and future lines.

The illustrative embodiments of the present invention improve networkplanning. Detailed knowledge of operating conditions permits betterforecasting of transmission line requirements and aids justification ofnew construction.

Illustrative embodiments of the present invention provide a smart gridsystem, method and apparatus that measure the conductor temperature toprovide feedback on the actual capacity, as well as other information,of a transmission line 30 (e.g. a power transmission line) at manypoints. The power transmission line may be overstressed, but it couldhave more capacity than that which is actually being used. Theillustrative system of the present invention can measure the wind speedand ambient temperature to determine the conditions along a powertransmission line that may be hundreds of miles long. Some parts of thewire of the power transmission line may be warmer than other partsbecause the power transmission line may run through a valley where thereis no wind, for instance, or due to other reasons. For example, ananemometer with no moving parts can be used to determine the coolingeffect of the wind.

The smart grid system is able to detect corona, even when it isintermittent, using audio detection of corona. The smart grid system isable to measure the current in the line. If it is determined that themeasured current is different than the current launched at a substation,there is a current leak or fault somewhere. The smart grid system isable to take a picture of the power transmission line and itssurroundings in order to visualize any ice, fallen trees, vegetation,and the like growing on the power transmission line, as well as saggingpower transmission lines, or even wildlife that may damage the powertransmission lines and smart grids.

The smart grid system can quickly determine if there is an immediate orlong term problem in the power transmission line and communicate to auser/technician. The smart grid system is easy to install, very robust,simple to administer, and does not require regular maintenance, such asreplenishing or recharging batteries. In addition, the system is costeffective and secure. The integrated web server in the smart grid dataacquisition device simplifies and reduces the cost of backend software.An improved radio protocol and routing algorithms are provided which areparticularly well suited for long runs with modest branching; however,they can be used for more general applications where Zigbee andZigbee-type technologies lack range or capacity.

The above-described exemplary embodiments of an apparatus, system andmethod in computer-readable media include program instructions toimplement various operations embodied by a computer. The media may alsoinclude, alone or in combination with the program instructions, datafiles, data structures, and the like. The media and program instructionsmay be those specially designed and constructed for the purposes of thepresent invention, or they may be of the kind well-known and availableto those having skill in the computer software arts. Examples ofcomputer-readable media include magnetic media such as hard disks,floppy disks, and magnetic tape; optical media such as CD ROM disks andDVD; magneto-optical media such as optical disks; and hardware devicesthat are specially configured to store and perform program instructions,such as read-only memory (ROM), random access memory (RAM), flashmemory, and the like. The media may also be a transmission medium suchas optical or metallic lines, wave guides, and so on, and is envisionedinclude a carrier wave transmitting signals specifying the programinstructions, data structures, and so on. The computer-readablerecording medium can also be distributed over network-coupled computersystems so that the computer-readable code is stored and executed in adistributed fashion. Examples of program instructions include bothmachine code, such as produced by a compiler, and files containinghigher level code that may be executed by the computer using aninterpreter. The described hardware devices may be configured to act asone or more software modules in order to perform the operations of theabove-described embodiments of the present invention.

Although exemplary embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions, and substitutions arepossible, without departing from the scope of the present invention.Therefore, the present invention is not limited to the above-describedembodiments, but is defined by the following claims, along with theirfull scope of equivalents.

What is claimed is:
 1. A data acquisition device for acquiring data froma transmission line comprising: at least one sensor for determining atleast one of a parameter and image associated with the transmissionline; a radio interface for communicating to at least one of amonitoring device and a neighboring data acquisition device via a radiocommunication link within a selected range; and a processing deviceconnected to the at least one sensor and the radio interface, theprocessing device being programmed to receive and process inputs fromthe at least one sensor, and to generate messages for transmission viathe radio interface; wherein the processing device is configured toparticipate in multi-hop communications via the radio communication linkby receiving messages generated by other data acquisition devices, anddetermining from information provided in each of the messages whichoperation to perform from among process the message, repeat the message,and ignore the message; wherein a network comprises a plurality of thedata acquisition device, each of the data acquisition devices beingassigned a unique address, the processing device being configured with aself-assembling process that automatically configures the dataacquisition device to communicate within the network of other dataacquisition devices and the monitoring device by receiving aconfiguration message transmitted from the monitoring device via theradio communication link, repeating the configuration message via theradio communication link, sending a reply message comprising itscorresponding address via the radio communication link in response tothe configuration message, receiving reply messages sent from other onesof the data acquisition devices, each of the reply messages comprisingthe corresponding address of the data acquisition device that generatedit, and determining from the reply messages the corresponding address ofeach of the data acquisition devices within its selected range; whereineach of the data acquisition devices in the network is configured toperform the self-assembling process to create a table comprising theunique addresses of the data acquisition devices in its selected range;wherein the unique address of each of the data acquisition devices is aMedia Access Control (MAC) address, the radio interface in each of thedata acquisition devices is a ZigBee radio interface customized toemploy the self-assembling process that assembles each of the dataacquisition devices into a communication network that obviates manualconfiguration of the radio interface in each of the data acquisitiondevices, each of the data acquisition devices being configured toautomatically generate the table with the MAC addresses of selected onesof the other data acquisition devices in its selected range.
 2. A dataacquisition device as recited in claim 1, wherein the informationprovided in each of the messages comprises a number of hopscorresponding to the number of times the message has been repeated byone of the data acquisition devices following its origination, theprocessing device being configured to increment the number of hops ineach of the messages before it is repeated.
 3. A data acquisition deviceas recited in claim 2, wherein the processing device is configured todetermine whether to repeat the message based on the number of hops andthe address included in the message.
 4. A data acquisition device asrecited in claim 1, wherein the configuration message is repeated, andthe processing device dynamically updates information relating to thedata acquisition devices based on the reply messages to theconfiguration message and stores the information in a memory device. 5.A data acquisition device as recited in claim 4, wherein the processingdevice can configure the information in the memory device upon power upand obviate pre-configuration.
 6. A data acquisition device as recitedin claim 1, wherein the data acquisition device further comprises aradio-to-ground communications interface for communicating with themonitoring device, the processing device being configured to aggregatedata about the other data acquisition devices from messages receivedfrom the other data acquisition devices via the radio communication linkand provide the data to the monitoring device via the radio-to-groundcommunications interface.
 7. A data acquisition device as recited inclaim 1, wherein the radio interface is assigned an encryption keydynamically.
 8. A data acquisition device as recited in claim 1, whereinthe data acquisition device further comprises a web server, theprocessing device being configured to send the message via email.
 9. Adata acquisition device as recited in claim 1, wherein the monitoringdevice is assigned an Internet Protocol address and configured toprovide a user with a Hypertext Markup Language (HTML) pagecorresponding to the data acquisition device that comprises the at leastone of a parameter and image obtained from the sensor.
 10. A dataacquisition device as recited in claim 1, wherein each of the dataacquisition devices comprises a corresponding Hypertext Markup Language(HTML) page.
 11. A data acquisition device as claimed in claim 1,wherein the transmission line is a power transmission line and furthercomprising a power supply for the data acquisition device comprising acurrent transformer connected to the transmission line and configured toextract power from a magnetic field generated by current in thetransmission line and provide direct current (DC) power to components inthe data acquisition device.
 12. A data acquisition device as recited inclaim 1, wherein the data acquisition device further comprises an audiocorona detector having a microphone and a processor comprising at leastone of the processing device and a processor associated with the audiocorona detector, the processor being configured to obtain audio inputsdue to respective corona events from the microphone, to process theaudio inputs to generate corresponding audio signatures representing thecorona events, and to compare at least parts of the audio signatureswith selected threshold characteristics.
 13. A data acquisition deviceas claimed in claim 12, wherein the processor is configured to sample anoutput of the microphone at least one of continually, periodically, andat selected times to obtain the audio inputs.
 14. A data acquisitiondevice as claimed in claim 12, wherein the processor is configured togenerate an alert if one of the audio signatures differs from at leastone of the selected threshold characteristics by a selected amount. 15.A data acquisition device as claimed in claim 1, wherein the sensorcomprises an ambient temperature sensor and an anemometer fordetermining wind speed using a measured ambient temperature from theambient temperature sensor and a reference temperature.
 16. A dataacquisition device as claimed in claim 1, wherein the data acquisitiondevice comprises a housing having a longitudinal axis that is parallelto a longitudinal axis of the transmission line, the housing comprisinga first end that is heated to a reference temperature by a heatingelement, and a second end enclosing an ambient temperature sensor, theprocessing device being programmed to determine wind speed using thedifference between a measured ambient temperature and the referencetemperature.
 17. A data acquisition device as claimed in claim 1,wherein the data acquisition device is configured to store a tablecomprising the unique addresses corresponding to a limited number of thedata acquisition devices in the network.
 18. A data acquisition deviceas claimed in claim 1, wherein the ZigBee radio interface in each of thedata acquisition devices is customized to be dynamically assigned anencryption key.